﻿#pragma warning(disable: 4996)
#pragma warning(disable: 6031)

#include <stdio.h>

void solve(int H) {
	double C = (H-100)*1.8;
	printf("%.1f", C);
}

int main()
{
	freopen("D:/Develop/GitRepos/MOOC/浙江大学/数据结构/201906/DataStructure/M2019秋C入门和进阶练习集/7-8.txt", "r", stdin);
	int H;
	scanf("%d", &H);
	solve(H);
	return 0;
}